Appearances of numerous high data rate wireless communication standards indicate that wireless communication has entered into an epoch with a rapid increase in reliability and capacity. Cooper's law explains the increase of wireless communication capacity well: “Wireless capacity has doubled every 30 months over the last 104 years”. For example, since American civil wireless communication system was spread and applied, wireless communication capacity has increased by nearly 1,000,000 times, wherein use of wider band has brought increase by 25 times, smaller time and frequency scheduling granularity has brought increase by 5 times, better modulation method has brought increase by 5 times, decreasing cell coverage area and transmission distance has brought increase by 1600 times. Huge benefits brought by decreasing cell coverage area are essentially brought by improving intensity of signals received and spatial frequency spectrum utilization rate, i.e. throughput on unit area. Therefore, appearance of a Femtocell which is a cell structure to provide in-building coverage with low cost and high data rate is of serious concern by researchers, operators and device manufacturers.
Macro-cells are regions of very large coverage area, coverage radius of which is about 1-30 km, and transmitting antennas of base stations usually are placed above surrounding buildings. Typically, there is no direct antenna between sending and receiving. While the Femtocells are wireless data access cells with low power and short distance, the coverage of which usually is 10-50 m, and takes wideband connections, such as fibers or xDSL (x Digital Subscriber Line, xDSL), as a return pass. Appearances of Femtocells earn widespread respect, and 3GPP LTE has incorporated it into R8 standard and named it Home Node B.
Surveys on use of mobile communications indicate that more than 50% voice communication and more than 70% data communication occurs in buildings. Meanwhile cities are growing fast, especially in China, where buildings in urban area are more intensive, and population density is also growing fast, and increasingly heavier loads has been caused, and the quality of coverage in building is also an urgent problem to be solved. Femtocells have achieved fast development in recent years, not only is the standardization very mature, but also various commercial networks and experimental networks are applied in many countries around the world. Therefore, in the near future, more and more families choose to install a Home Node B in home, some office buildings and shopping centers also choose to arrange a Home Node B to improve the coverage in buildings, whereby intensive Femtocell arrangement is possible to occur. In order to utilize precious frequency spectrum resources better, by multiplexing frequency on space to maximize system capacity, it's a better choice to overlapping deploy frequency resources of Femtocells and traditional macro-cells, but it's certain to bring interference between Femtocells. Under extreme condition, two Femtocells are placed on the two sides of a wall respectively and use the overlapped resources. Therefore, if there is no efficient interference suppression algorithms and resource allocation algorithms, communications of subscribers in a Femtocell edge cannot be ensured and it leads to insufferable dropping rate.